CVE-2025-66647Public exploitNetwork attack vector

Remote device crash via unchecked fragment copy

Published Dec 17, 2025 · Updated Dec 17, 2025

Buffer overflow in RIOT before 2025.10 allows remote attackers to crash devices by sending crafted IPv6 fragments. The gnrc_ipv6_ext_frag_reass function uses memcpy to place a larger second offset-zero fragment into the small reassembly buffer allocated for the first fragment without checking its capacity. The gnrc_ipv6_ext_frag module must be enabled and accept arbitrary IPv6 packets; an OS crash is demonstrated, while arbitrary-memory overwrite and code execution remain unproven.

CVSS severity9.8
Critical
EPSS probability0.97%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in RIOT before 2025.10 allows remote attackers to crash devices by sending crafted IPv6 fragments. The gnrc_ipv6_ext_frag_reass function uses memcpy to place a larger second offset-zero fragment into the small reassembly buffer allocated for the first fragment without checking its capacity. The gnrc_ipv6_ext_frag module must be enabled and accept arbitrary IPv6 packets; an OS crash is demonstrated, while arbitrary-memory overwrite and code execution remain unproven.

The record

CVE
CVE-2025-66647
Published
Dec 17, 2025
Updated
Dec 17, 2025
Vendor
RIOT-OS
Product
RIOT
Classifications
CWE-120, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 17, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 17, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2025.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

RIOT-OS · RIOTversion=< 2025.10

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
1.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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